This invention generally relates to cutting layers of semiconductor materials from substrates that may be used for electronics, optics or optoelectronics. In particular, the invention relates to a device for automatic high-precision cutting of a semiconductor layer from a substrate that includes a weakened area and an annular notch. The device includes cutting means and means for maintaining the position of the assembly that includes the source substrate.
It is noted that “cutting” means dividing a single element, substrate or an assembly into two separate parts, and guaranteeing that the parts do not recombine. This type of cut is included within the framework of a substrate that includes a weakened area.
Substrates are usually in the form of disks called “wafers”. Wafers may be made from a semi-conducting material such as silicon. It is known that a weakened area can be formed inside a wafer along a plane that is parallel to the principal faces of the wafer. The weakened area may be made by implantation of ions bombarded on the wafer surface. The ions create a weakened layer within the thickness of the wafer to delimit an upper region (in this text corresponding to the source substrate) and a lower region adjacent to the ion source (in this text corresponding to the layer that will be cut). U.S. Pat. No. 5,374,564 describes an example of such a process to make thin layers. Devices and processes are used to build up layers (thin or not) that may be transferred to a target support from a source substrate.
The weakened area can also be made by any known means. For example, an intermediate region made of porous materials can be built up between two regions of dense material, by forming an oxide layer buried in a substrate (for example an SOI (Silicon On Insulator) type substrate), or by bonding two layers, the bonding area corresponding to the weakened area.
A operator can manually make a cut at the weakened area to form two separate elements from the source substrate and the layer. But calling in an operator sets a limit to the layer production rate. Furthermore, it is not certain that the operation can be reproduced from substrate to substrate. Automatic cutting devices and processes are known to overcome the above-mentioned disadvantages. U.S. Pat. No. 6,418,999 describes one example of such a device and process. The device described in this patent uses a water jet impacting on the edge of a wafer held in place in two principal faces, to attack a weakened area and divide the wafer into two parts. But the design and operation of such a devices are relatively complex. In particular, a specific type of holder is necessary so that each of the two faces of the wafer are held to permit a given separation of the two parts of the wafer. Furthermore, the maintaining means or holder must also rotate the wafer so that its entire periphery is attacked by the water jet, which further increases the complexity of the design and operation of the device.
Document EP 989 593 also divulges a layer cutting device and process. But once again, a complex arrangement is necessary, in particular to maintain the position of the two parts of the wafer that are to be separated.